(deleted)
Didn't Psion use H8?
Hitachi's microprocessors became part of Renesas. You might be able to find additional documentation on the Renesas site
There's a gcc for H8: H8 Legacy Toolchains | Open Source Tools for Renesas
Datasheet: https://www.datasheets360.com/pdf/864743618009682633
(Your photo shows 84pin plccs, BTW.)
My advice: throw them away. There isn't enough time in the world to spend working on dead-end architectures, without even hobbyist history behind them. If you want to play with something old, get a Z80 or 8051 (the 8051 architecture is still in common use.)
Also, those are PROM-based chips, not flash, and not eraseable, so you get ONE chance to program them (assuming that there isn't already code in them...) (and it probably requires a programmer with weird programming voltages.)
Well, there is an “active” forum for this hitachi H8 series:
http://renesasrulz.com/other_products/h8/f/h8---forum
But even to get to the stage of creating a hand assembled version of the “blink sketch” and getting it loaded and running would be a considerable achievement.
notgwb:
What to do with a ton of old Hitachi H8 MCUs?
Nail them to a wall and call it art ?
westfw:
Hitachi's microprocessors became part of Renesas. You might be able to find additional documentation on the Renesas site
There's a gcc for H8: H8 Legacy Toolchains | Open Source Tools for Renesas
Datasheet: https://www.datasheets360.com/pdf/864743618009682633
(Your photo shows 84pin plccs, BTW.)My advice: throw them away. There isn't enough time in the world to spend working on dead-end architectures, without even hobbyist history behind them. If you want to play with something old, get a Z80 or 8051 (the 8051 architecture is still in common use.)
Also, those are PROM-based chips, not flash, and not eraseable, so you get ONE chance to program them (assuming that there isn't already code in them...) (and it probably requires a programmer with weird programming voltages.)
A 6809 with a bunch of IO ports, timers, etc (microCONTROLLER) stuff and a larger, flat address space would be heaven.
BTW I have had some success erasing OTP memory using low power X-ray radiation. I also tried gamma... not good it destroyed the processor (68HC11 devices).
Yes, gamma. I had access to a professor who had a cobalt-60 source and he would irradiate chips for me for the number of seconds I asked for. Gamma is too "hot" - it nukes the whole chip.
krupski:
Yes, gamma. I had access to a professor who had a cobalt-60 source
Now that's a neat toy! How beefy of a source was it? 1 uCi sources are readily available and safe to handle, but Co-60 sources powerful enough to be "self-protecting" exist (used in industry for sterilization, and in medicine for cancer treatment).
(Put another way: the special-purpose programmer you need to program your chips, plus the socket, plus the sockets for your PCBs, will end up costing you $50-100. For that price you can buy 75 modern chips that are more powerful, easier to program (language-wise, IDE-wise, and electrically) that aren't a technological dead end (or not as much of one, anyway.)
For example, you can get 50 ATmega4809 chips in 40pin DIP for about $2 each. Cheaper if you can deal with the fine pitch SMT packages.
Looks like the general consensus is sell those on eBay as NOS and get reprogrammable chips that can be useful
DrAzzy:
Now that's a neat toy! How beefy of a source was it? 1 uCi sources are readily available and safe to handle, but Co-60 sources powerful enough to be "self-protecting" exist (used in industry for sterilization, and in medicine for cancer treatment).
Don't think I ever knew how much "power" the Co60 source had.
It was a large (around 12 inches) lead lined steel cube, and it had a remote control "shutter" that would expose or cover the source. There was some sort of elaborate lead shielding in it where shield material overlapped to prevent any "line of sight" leakage.
I was scared to death of the thing... I handed the Prof. the chips with a note as to how much to irradiate them and scurried off in the other direction.
I want nothing to do with anything shorter wavelength than UV... 
Edit to add: Years ago I was an engineer at a medical device manufacturer. We used ethylene oxide to sterilize the lots.
The ETO (ethylene oxide) was an explosive compound when pressurized and in liquid form. So, the ETO we used was called 88/12 because it was 88% ETO and 12% freon to render it "safer".
The ETO came as large gas cylinders on a pallette, all strapped together and connected to a common manifold. Since the ETO and freon had different density, it was supposed to be agitated (mixed) once in a while.
Being on a pallette and all tied together, it was obviously impossible to mix. So we flirted with explosive disaster on a daily basis. Thankfully my office was nowhere near the sterilizer area.
The point here is (I'm getting to it) the company decided to look into gamma sterilization. Knowing how slipshod they were with the ETO, I said "If they start doing gamma I'm outta here". Well, they eventually did go to gamma, but I left there before then for other reasons.